#define _CRT_SECURE_NO_WARNINGS 1
class Solution {
public:
    string longestPalindrome(string s) {
        int n = s.size(), ret = 0, begin = 0;
        vector<vector<bool>> dp(n, vector<bool>(n));
        for (int i = n - 1; i >= 0; i--)
        {
            for (int j = i; j < n; j++)
            {
                if (s[i] != s[j]) dp[i][j] = false;
                else if (i == j || i + 1 == j) dp[i][j] = true;
                else if (dp[i + 1][j - 1]) dp[i][j] = true;
                else dp[i][j] = false;
                if (dp[i][j] && ret < j - i + 1) ret = j - i + 1, begin = i;
            }
        }
        return s.substr(begin, ret);
    }
};